Etchant rinse method

ABSTRACT

Residual etchant, such as acid and the like remaining on articles such as printed circuit boards that have been etched, contains a metallic chemical component, such as copper. When this residual etchant is rinsed from the articles (such as printed circuit boards), it contaminates the water of the rinse. The chemical replacement of copper ions in the rinse with aluminum ions by passing the rinse through a basket filled with aluminum turnings, and recycling the rinse thus passed back for reuse at the rinsing station continuously renders the rinsing water free of copper, to permit periodic discharge of the rinse water to sewage or the like.

Goffredo et a1.

1 1 ETCHANT RINSE METHOD [751 Inventors: Daniel L. Goffredo, Riverton.N.J.;

John Alfred Dunkelberger, Jr., Centre Hall. Pa.

1731 Assignee: Chemcut Corporation, State College, Pa

|22| Filed: (Jet. 29, 1974 l21| Appl No: 518,564

Related U.S. Application Data [621 Division of Ser. No. 191L136. ()cL 1819714 |52| 1.1.8. Cl. 134/13; 134/10; 156/19; 210/38 [51] Int. (1. mmB08B 3/02; 130813 3/10; B08B 7/04 [51%] Field of Search r. 134/10 l3109,1ll l31 134/151 199.83; 156/19, 345; 210/38 287, 433:75/109 101 BE;204/32 R 35 R [Sfil References Cited UNITED STATES PATENTS 24401344/194H Zademach et a1. .1 134/111 X 3.081774 3/1963 Benton et a! 1.134/151 X 1451 Sept. 16, 1975 Primary Exumim'rS. Leon Bashore AssistantExuminm-Marc L. Caroff Alturney, Agent or Firm Paul & Paul [57 IABSTRACT Residual etchant, such as acid and the like remaining onarticles such as printed circuit boards that have been etched, containsa metallic chemical component, such as copper. When this residualetchant is rinsed from the articles (such as printed circuit boards), itc ntaminates the water of the rinse. The chemical replacement of copperions in the rinse with aluminum ions by passing the rinse through abasket filled with aluminum turnings. and recycling the rinse thuspassed back for reuse at the rinsing station continuously renders therinsing water free of copper, to permit periodic discharge of the rinsewater to sewage or the like.

4 Claims, 2 Drawing Figures PATENTEU 3 905 827 SHEET 1 [IF 2 ETCHAN'IRINSE METHOD This is a division of application Scr. No. 190.136 filedOct. I8. I97].

BACKGROUND OF THE INVENTION In the art of etching printed circuit.boards and the like. it has been commonplace to rinse acid etchants fromthe printed circuit boards. for purposes ofcleaning" the acid from theboards. in order that the boards may be subsequently handled bypersonnel. and also to assure the termination of the etching process. oncop per components of the board. Such washing or rinsing hasconventionally been done by spraying the boards with a water rinse. andeither contmuously or periodi cally replacing the water rinse. with usedwater rinse being discharged to sewage or the like. However. such usedwater rinse in accordance with the above mentioned prior art techniqueshas contained copper ions therein. and such has been found to causeundesirable ecological effects upon streams. waterways and the like.into which the used rinse eventually finds its way from sewage.

Furthermore. the copper contained within the acid rinsed off the boardsin accordance with these prior art techniques has been permanently lost.

SUMMARY OF THE INVENIION The present invention is directed towardproviding an apparatus and method whereby recycling of the rinse wateris possible without building up an undesir-- able level of copperconcentration in the rinse water. and whereby the rinse water is notcontaminated by copper. so that the same may be discharged into cowventional sewage lines. streams. etc. without producing damagingenvironmental effects. A portion of the rinse water being delivered tospray nozzles passes from the reservoir of rinse water to and through aparticulate material (preferably aluminum turnings). and the rinse wateris dispersed therethrough. eventually being returned to the rinsereservoir. During its passage through the aluminum turnings. a chemicalreplacement of copper ions in the rinse is effected, by replace mentwith aluminum ions. with the copper ions being reduced to metalliccopper, and with the aluminum being oxidized and flowing into solutionin the rinse water. The rinse water thus accumulates an aluminum ionconcentration, which may periodically be discharged as desired. withoutproducing undesirable environmental effects.

Accordingly. it is a primary object of this invention to provide a novelmethod of treating etchant rinse wa* ter.

It is a further object of this invention to provide a novel method ofreplacing copper ions in etchant rinse water with aluminum ions.

It is another object of this invention to provide a novel apparatus forrinsing etchant reactants from articles that have been etched. whereinsuch apparatus involvcs chemical replacement ofunwanted metallic ions inthe rinse medium.

Other objects and advantages of the present invention will be readilyapparent to those skilled in the art from a reading ofthe followingbricfdescriptions of the drawing figures. detailed description of thepreferred embodiment. and the appended claims.

Til

IN THE DRAWINGS FIG. I is a transverse sectional view through theseveral components of a rinsing apparatus of this invelr tion.

FIG. 2 is a longitudinal sectional view through a por tion of therinsing apparatus illustrated in FIG. I. and illustrating the manner inwhich the rinse is sprayed onto printed circuit boards or the likepassing through a rinse chamber from an etching chamber or the like.

Referring to the drawings in detail. reference is first made to FIG. 2.wherein an upstream chamber It) is il lustrated. as comprising anetching chamber. or if de sired. a chamber for first physically removingetchant from printed circuit boards II or the like conveyedtherethrough. by means other than water spraying. The printed circuitboard It for which this apparatus has been developed. is then deliveredinto a rinsing chainber I2, passing along a plurality of driven rollersI3. which rotate in a clockwise direction as viewed in the illustrationof FIG. 2. for movement of the printed cir cult board II in thedirection of the arrow l-l of FIG. 2. through the chamber 12 fore\entual discharge through the outlet [3 thereof. to a drying station orthe like.

The board 1]. upon its delivery to the chamber 12 may have residualcomponents of an etching acid. such as ferric chloride thereon. that hasbeen used to etch unmasked copper portions of the printed boards. andsuch residual etchant thus contains a certain copper content.

The board ll then passes between upper and lower circuit sets of spraynozzles 15 and I6, that are supplied with water under pressure. forspraying the board I I through a certain /.one such as that indicated inFIG. 2. with the zones of spray of the nozzles combining transverscly ofthe machine, in order to completely spray a board ll carriedtherebetween. as will be more clearly apparent with reference to theillustration of FIG. I. The upper spray nozzles 15 are connected torinse water header 1?, and the lower spray nozzles lb are each connectedto a lower rinse water header [8. with the headers l7 and 18 beingsupplied with rinse water from a common delivery line 20. After sprayingof the board II with rinse water passing through the nozzles 15 and If),the rinse water 21 drops into a reservoir 22. and such rinse water 21and the reservoir 22 now has a slight concentration of copper ionstherein. Rinse water 21 is delivered from a chamber 22. by a pump 23. orother suitable device. which receives the rinse water 21 at a lowerinlet 24 thereof. and delivers the same through an outlet line 25, withthe pump 23 being driven by an electrical motor 26 or the like disposedoutwardly of the chamber 22, but connected to the pump 23 through arotatable shaft 27 that passes into the chamber 22 from outside thereof.to drive the sub merged pump 23.

Rinse water is thus delivered through the line 25, out wardly of thechamber 22. with the delivery line 25 being bifurcated at the piping tcc2). with some of the rinse water being delivered to the spray nozzles I5and 16. through the line 20. and some of the rinse water being deliveredthrough a replacement chamber 28. and back into the reservoir 22 througha return line 30. selectively openable upon actuation of a switch SI orthe like. as desired. whereby rinse water is delivered to thereplacement chamber 28, as a parallel loop to that delivered to thespray nozzles 15 and lo. Thus. rinse water enters the replacementchamber 28. being delivered thereto by a suitable piping line 32, andpassing through a generally open shut-off switch 33. entering thereplacement chamber 28. through the bottom 34 thereof, at a centralopening thereof, for passage outwardly of a plurality of holes 35, orother suitable perforations in the outer surface of a hollow cylindricalupstanding standpipe 36. as illustrated in H6. l.

A removable tank 37 is provided, inwardly of the replacement chamber 28,the bottom of which has a blind hole therein for facilitating thedisposition of the tank 37 over the standpipe 36, and with the sides ofthe blind hole 38 in the tank 37 facilitating the passage inwardly ofrinse water into the interior 40 of the tank. as such rinse water passesthrough perforations 35 of the standpipe 36. The tank 37 is constructedas a basket. with the outer cylindrical surface 4| thereof also beingperforate, and with the basket being filled with a particu late materialsuch as aluminum turnings whereby the rinse water 2] delivered throughthe line 32 will pass through the aluminum turnings, to be dischargedthrough the tank 37, but passing through perforations in the outer wall41 thereof. It will be noted that the outer surface of the tank 4] isspaced inwardly of the inner surface of the chamber 28, to form anannular void therein, for passage of water upwardly, inasmuch as thewater is under pressure from the pump 23, and with the water thus beingredelivered through the line 3" as aforesaid. into the chamber 22.

The tank 37 is also provided with a handle 43 whereby the same mayreadily be grasped and removed from its position over the standpipe 36.upon opening the lid 44 of the chamber 28. whenever the concentration ofcopper within the aluminum turnings necessitates replacement of the tank37, or of the turnings carried therein.

It will be apparent from all of the foregoing, that during the passageof the rinse water through the aluminum turnings within the tank 37, thedissolved copper content within the rinse is chemically replaced withaluminum from the aluminum turnings, and the copper ions removed fromthe rinse are reduced to metallic copper and aluminum is oxidized, goinginto solution in the rinse water. The water reservoir thus remainsextremely low in copper ion concentration. but will progressivelyincrease in aluminum ion concentration. Upon the reservoir 22 achievingan objectionable level of aluminum ion concentration, the rinsc water 21therein may be discharged to sewage or the like, without causingcontamination of sewage lines, waterways, or the like.

The herein discussed invention is significant in that it provides asimple and low cost means of eliminating objectionable copper ions frometchant rinse water. Accordingly. a highly desirable anti-pollutionfeature is encompassed by the present invention, which replaces copperion concentration in rinse water with more acceptable aluminum ions.

While displacement reactions themselves are previously known, forremoving copper from solution generally. and wherein such processes aregenerally known as cementation". in the mining industry, for example,

the use of replacement ions to resolve a heretofore dif ficult pollutionproblem for the etching industry. and particularly for the industryrelating to the etching of printed circuit boards is highly desirable.

It will also be apparent that other types of chemical replacement may beeffected. in lieu of using aluminum particles within the tank 37. Forexample, iron filings, magnesium. or any other metal above copper in theelectromotive series. or any other substance that will effect thedesired ion exchange. preferably with regard to its adaptability toachieving the other desired ends of this invention as set forth herein,may be utilized within the tank 37, if desired, for replacement ofcopper ions with iron ions in the solution.

Another feature of this invention is that the process permits continuousreplacement of copper ions in the rinse water, by permitting continuousremoval, by displacement reactions onto the aluminum surfaces of theparticles within the tank 37. it will, however, be appar' ent that theparallel loop arrangement illustrated in FIG. I is not to be construedas limiting, in that rinse water 21 from the tank 22 may pass seriallyfirst to the tank 37. and then to the spray nozzles 15 and 16. ifdesired. or the converse.

It will be apparent from the foregoing that various modifications may bemade in the details of construction of the apparatus of this invention.as well as in the method of use thereof, all within the spirit and scopeof the appended claims.

What is claimed is:

l. A method of removing residual chemical etchant from articles such asprinted circuit boards and the like that have been subjected to etchingof copper portions thereof. comprising the steps of conveying etchedarticles along a predetermined path, spraying the articles with a waterrinse during their conveyance along the path and thereby accumulating asignificant concentration of copper ions in the rinse water. collectingthe rinse water in a reservoir, providing a tank of particulatematerial. which material is capable of replacing copper ions in therinse with its own ions, continuously delivering rinse water from thereservoir simultaneously to the tank for transfer through theparticulate material wherein the ion replacement is effected and forspraying the articles, and continuously recycling rinse water that hasbeen subjected to the ion exchange to the reservoir, for reuse inspraying.

2. The method of claim 1, wherein the particulate material comprisesaluminum particles for replacement of copper ions in the rinse waterwith aluminum ions.

3. The method of claim 2, wherein rinse water delivered to the tank ispumped thereto from the reservoir concurrently with pumping of rinsewater for spraying. through a common bifurcated delivery line. andwherein rinse water is delivered directly to the reservoir following theion exchange.

4. The method of claim 1, wherein the rinse water is periodicallydischarged to a sewage line and replaced as the ion concentration of thereplacing ions from the particulate material in the rinse water reachesa predetermined level.

1. A METHOD OF REMOVING RESIDUAL CHEMICAL ETCHANT FROM ARTICLES SUCH AS PRINTED CIRCUIT BOARDS AND THE LIKE THAT HAVE BEEN SUBJECTED TO ETCHING OF COPPER PORTIONS THEREOF, COMPRISING THE STEPS OF CONVEYING ETCHED ARTICLES AONG A PREDETERMINED PATH, SPRAYING THE ARTICLES WITH A WATER RINSE DURING THEIR CONVEYANCE ALONG THE PATH AND THEREVY ACCUMULATING A SIGNIFCANT CONCENTRATION OF COPPER IONS IN THE RINSE WATER, COLLECTING THE RINSE WATER IN A RESERVOIR, PROVIDING A TANK OF PARTICULATE MATERIAL, WHICH MATERIAL IS CAPABLE OF REPLACING COPPER IONS IN THE RINSE WITH ITS OWN IONS, CONTINUOUSLY DELIV-
 2. The method of claim 1, wherein the particulate material comprises aluminum particles for replacement of copper ions in the rinse water with aluminum ions.
 3. The method of claim 2, wherein rinse water delivered to the tank is pumped thereto from the reservoir concurrently with pumping of rinse water for spraying, through a common bifurcated delivery line, and wherein rinse water is delivered directly to the reservoir following the ion exchange.
 4. The method of claim 1, wherein the rinse water is periodically discharged to a sewage line and replaced as the ion concentration of the replacing ions from the particulate material in the rinse water reaches a predetermined level. 